Choosing and Using the Right Dehumidifier
To Dry Out Your Home
Dehumidifiers are just one more way that man has taken control of his
Basements can be dark, damp, moldy places. But they can be used for
living and storage by controlling the amount of moisture in the air... a problem
common to all but the driest climates. Dehumidifiers remove moisture from
air, improving the usefulness of basements by controlling the dampness and the
potential damage to your home and possessions.
So unless you prefer to use your basement mostly for
growing mushrooms and designer mildew, there should be a dehumidifier in your
What is a dehumidifier and how does it work?
A dehumidifier is essentially a refrigerator that forgot to get fully
dressed. Really. The basic mechanical function of a dehumidifier is the same as
a refrigerator. Compression and expansion of a gas is used to lower the
temperature of metal coils to freezing temperatures.
However, instead of the cooling action being directed into a
closed box, a dehumidifier is designed to blow warm moist room air over
these cold coils. The moisture in the room air condenses on the coils to
become liquid water. The water then drips into a drip collection pan, or
to a drain. The room air, now freed of much of its moisture, returns to
the room slightly warmer than it was.
Dehumidifiers are controlled by a device known as a humidistat. This is
an adjustable rotary switch which detects moisture in the room's air. It
automatically turns the dehumidifier on or off as it is needed, based on
the setting you choose. If you wish, you can set the dehumidifier to the
maximum setting for continuous operation.
Why would I want to purchase one?
If you store anything of value in your basement or if you use your basement
as living space, it is important to keep the moisture level low. Unlike the rest
of your home, the parts of your foundation that are below ground level, or
"grade", is constantly in contact with moisture from the earth
outside. Though some homes have adequate vapor and water barriers installed
outside their foundations, many older homes have none.
This moisture can cause mildew and mold growth, which can cause permanent damage to furniture of all types,
photos, carpets, and virtually anything except the dog. It is a sad fact that
every year people unknowingly destroy their valuable possessions by not taking
steps to lower the level of moisture in their basement's air.
How big a dehumidifier should I buy?
Good question, but the answer is unclear. There are arguments for both large
and small dehumidifiers. Large ones remove moisture faster, so they operate for
shorter periods of time. Larger dehumidifiers also have a larger water storage
capacity, so you need to empty them less often (unless you install an automatic
pump, making emptying unnecessary).
On the downside, more electricity is used per hour to run
a larger dehumidifier, with its larger fan and compressor. And since more electricity is used at
"start-up" than during any other time in the cycle, some of the
apparent cost benefits of large size are lost since it will cycle on and off
more frequently. Larger units are
also more expensive to purchase, so there may be little or no benefit to buying an
oversized unit for most people. In my own experience of owning
dehumidifiers for over 30 years, I look at the manufacturer's specs and buy a
unit one size larger since my cynical view is that they most likely overestimate
the power of the smaller units and the fact that testing does not take into
account moisture absorbing furniture and the other idiosyncrasies of your own
Bigger can at times really be better! The advantages of size are most
noticeable when dehumidifying a large area. A small dehumidifier may run
continuously and still never lower the humidity to an acceptable level. A
larger unit, by dehumidifying a larger amount of air per hour, can keep up with
the demands of a large room.
Do I need someone to install it?
That depends. Since the condensed water drips from the coils it has to go
somewhere. If your basement has only a small moisture problem and you don't mind
carrying the drip pan outside or to a sink, just put the dehumidifier on the
floor and plug it in. It will shut off automatically when the drip pan is
full... hopefully. This is not the most fun way to live with a dehumidifier...
the drip pans (especially on the larger units) hold a lot of water and can be
quite heavy when full. Actually I'm still waiting for a model that will call me
so I don't have to keep checking. (By name!)
The solution nonpareil is to install your dehumidifier so that it is
self-draining. If you have a sink or toilet in the basement, or even a lowly
floor drain, place the dehumidifier on a table or a shelf and run a hose from
the drip pan to the drain.
If you do not have a drain you can still make your unit self-draining, but
things get more complicated. Since dehumidifiers do not pump water upwards, you
may need to install a sink pump. This is a special enclosed pump designed for
non-sewage use to move waste water upwards to your plumbing drain pipes. It will
work with sinks, washing machines, water softeners, and... yes, dehumidifiers.
Here you go, guys! Always wanted that sink in the basement, right? Now you
have a great excuse... uhh... logical reason!
Another alternative is to put the dehumidifier on a table or shelf so that it
can drip into a large container, such as a 5 gallon bucket on the floor. This
will decrease your number of trips for sure, and will probably give you forearms
like Popeye from carrying that heavy bucket upstairs. The only drawback... this
is a biggie... is that the dehumidifier will have no way to know if the bucket
is full, so it will continue to run even after the bucket is full and
overflowing all over the new carpet! So, when you go on vacation,
disconnect the hose from the drip pan and screw a garden hose cap on the hose
pan's nipple (ouch!). Then, you can at least run the dehumidifier until the pan
Should I use a dehumidifier year round?
That depends on the temperature of your basement and your local
climate. Dehumidifiers do not function well at lower temperatures,
so under 65 degrees it is almost a waste of money to run them. Plus, as the air
temperature drops, the risk of freezing the coils increases (read the next
question for more on freeze-ups). If you heat your basement, the warm air will
move moisture from the basement to the house above, keeping the humidity lower
in the basement and slightly humidifying the rest of the house.
In areas where the ground is frozen for most or all of the winter, the amount
of moisture that will migrate through the basement floor and walls will drop
dramatically in the winter, so the need for dehumidification decreases. However,
if you live in a temperate area, and your basement is not heated, you may have
to run the dehumidifier year round.
Is there any maintenance to perform?
You should check the coils at least seasonally and keep them clear of dust
and dirt. If the unit has a removable front cover, there may be a foam filter
inside that should also be cleaned.
The purpose of this cleaning is two-fold. First, dust and dirt can insulate
the coils from the room air, decreasing the efficiency of the dehumidifier.
Secondly, this same dirt will get damp and possibly freeze. Freezing is the most
damaging thing that can happen to your dehumidifier because it will run
continuously but not dehumidify the air. This will lessen the life of the unit
and lighten your purse when the unit suffers a premature death! Not to mention
the bill your smiling utility man will hand deliver with a "Thank You"
note from the electric company.
What brand should I buy?
I don't do product testing. Not that I wouldn't enjoy doing it, but I have
toasters to clean and socks to sort.
When I purchase a new product, especially an expensive appliance, I always
ask myself, "If this product needs service, or parts, can I get them
locally?" I also ask myself, "Will this company be in business in a
year... or 5 years?" So I tend to make these types of purchases from
established local dealers, or choose a brand name that I have had experience
with, either with other of their products or based on their reputation. Then...
I go bargain hunting!
You can, of course, try to find back issues of product evaluations in
magazines but I have found that to be a fruitless exercise most of the time. My
experience has been that the reports they give are often for products and models
that you can't find in local stores. It's telling and a sign of the times that
so many companies don't keep their products on the shelves long enough for us to
figure out if they are any good! Go figure.